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Discussion Starter · #1 ·
Hi all,

I have got the following weird boost problem:

When I fit new spark plugs, the car goes like dream, but after a while (not even 1000km) it will reduce boost back to base boost after 3k rpm

Peak boost is around 1.05 bar, it will then settle down to 0.9-1.0 bar and will then reduce and reduce untill it's at base boost around 3k.

I have made a little video of the gauge in 5th gear:

http://users.pandora.be/saabtuning1/images...voort%20025.avi

Base boost is set at 0.45 bar, wastegate actuater has not fallen off and I already tried three different DI cassettes combined with new spark plugs. Right now, I have no idea anymore

All I know for sure is that when I fit new spark plugs, the car will go like a dream again, but only for a couple of 100km...


Edited at Marky's request.
 

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My carly used to do that until i fitted a new wastegate actuator. This solved the problem, but it wouldnt explain the full boost with new plugs.
Trionic uses the plugs to gather data - are the older plugs somehow causing wrong readings?
I'll let wiser heads answer now!
 

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Weird,

It doesn't look like APC function as its too slow and smooth.

I'd go with:

wastegate blowing open (poos spring pressure)
dud APC controller valve (dead and part blocked?)
Air leak (dump/recirc valve?)

Andrew
 

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Discussion Starter · #4 ·
Indeed very weird

Will replace the actuator tomorrow (have a spare TD04), Although it seems strange as it does function properly with new sparkplugs, the same for the APC solenoid

Car has an atmospheric dumpvalve, vacuum lines are all replaced not long ago.

Can bad fuel do something like this? I always go to the same petrol station, and the car has been acting like this since I got it, 20000km ago
 

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It's a bit blurry for diagnoses, but that stuff looks like the deposits left by MMT. I had a similar problem with T7 after a few tanks with high concentrations of MMT, which is an octane booster.
 

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That looks awful. Are you using any fuel additive or octane boost? It may be a good idea to use fuel from a different petrol station for a while to see if that is what is causing the rusty colour.

I don't think a blown head gasket would cause that colouring, would it?
 

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Discussion Starter · #10 ·
I'm not using any fuel additives or octane booster. Just the normal 98 fuel at our local petrol station.

We also have a BP and a Total Fina station here, does any of the two have your preference?

Also, what is the ideal gap of the spark plugs? The book says 0.9-1.1, so I used 1.0
 

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I agree with Bill. There is something fouling the plugs and that is your boost problem. I think it may be possible that coolant from a possible blown head gasket is causing it? I am also willing to bet you can just use a wire brush on the tip and electrode of the plugs and it will run good.
 

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ok lets try and work it out
Trionic uses the plug to sense ionisation
it puts a weak current across the gap
now if some rogue ions are interfering with this then you will screw up the sensing system
That looks awfully like ferrous oxide on your plugs (or some other metallic oxide )
so methinks the fuel/fuel system is to blame
Maybe your fuel tank is rusting /petrol station tank ...
fuel filter has caught the big stuff but small particles are getting through..enogh to screw up the spark plugs perhaps
First of all I would change the fuel filter (under a tenner)
do not throw it away but cut it open and have a look...
If ok then suspect the fuel station..change brands
 

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Also, there shouldn't be any problem with a 1,0 mm gap. The gap will increase over time, so it's best to stay below the upper limit. That being said, I always change mine every year, or 12k miles, whichever occurs first.
 

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Originally posted by BillJ:
[qb]That looks awful. Are you using any fuel additive or octane boost? It may be a good idea to use fuel from a different petrol station for a while to see if that is what is causing the rusty colour.

I don't think a blown head gasket would cause that colouring, would it? [/qb][/b]
Looks an awfull lot like my plugs after some very effective octane booster which had high concentrations of MMT:



I had similar boost problems as a result, though my problems weren't quite as extreme.

Adrian W~
 
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